Overwriting database file with another non-empty one

Question

I'm trying this to overwrite the file:

File file = new File(importDir, dbFile.getName());
DataOutputStream output = new DataOutputStream(
new FileOutputStream(file, false));                 
output.close();

But it obviously overwrites an old file with an new empty one, and my goal is to owerwrite it with the content provided by file

How do I do that correctly?

score 1 · Answer 1 · edited May 23 '17 at 12:20

1

Unfortunately, such simple operation as file copying is unobvious in Java.

In Java 7 you can use NIO util class Files as follows:

Files.copy(from, to);

Otherwise its harder and instead of tons of code, better read this carefully Standard concise way to copy a file in Java?

edited May 23 '17 at 12:20

Community

1
1

answered May 14 '12 at 17:56

mishadoff

10,719
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Android is not comparable to Java 7, and does not appear to have java.nio.file – Chris Stratton May 14 '12 at 18:26
I didn't take into account android tag – mishadoff May 14 '12 at 20:34

score 0 · Answer 2 · answered May 14 '12 at 17:45

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    String str;
    System.out.print("Enter a file name to copy : ");
    str = br.readLine();

    int i;
    FileInputStream f1;
    FileOutputStream f2;

  try
  {
    f1 = new FileInputStream(str);
    System.out.println("Input file opened.");
  }
  catch(FileNotFoundException e)
  {
    System.out.println("File not found.");
    return;
  }

  try
  {
    f2 = new FileOutputStream("out.txt");    //    <---   out.txt  is  newly created file
    System.out.println("Output file created.");
  }
  catch(FileNotFoundException e)
  {
    System.out.println("File not found.");
    return;
  }

  do
  {
    i = f1.read();
    if(i != -1) f2.write(i);
  }while(i != -1);
  f1.close();
  f2.close();
  System.out.println("File successfully copied");

i hav not read about database file in your question, so I posted this answer here — Chintan Raghwani, May 14 '12 at 17:49

score 0 · Answer 3 · edited Jun 20 '20 at 09:12

0

You can use

FileOutputStream fos = new FileOutpurStream(file);

fos.write(string.getBytes());

constructor which will create the new file or if exists already then overwrite it...

edited Jun 20 '20 at 09:12

Community

1
1

answered May 14 '12 at 17:50

NullPointerException

3,978
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yeah well... there is no string to getBytes on it – Jacek Kwiecień May 14 '12 at 17:51
i think you can't copy directly file.. instead you have to read it line by line and write it to other file... – NullPointerException May 14 '12 at 17:57

score 0 · Accepted Answer · answered May 14 '12 at 20:20

0

For my purposes it seems that the easiest way is to delete file and then copy it

            if (appFile.exists()) {
                appFile.delete();
                appFile.createNewFile();
                this.copyFile(backupFile, appFile);

answered May 14 '12 at 20:20

Jacek Kwiecień

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Overwriting database file with another non-empty one

4 Answers4